Hitch assemblies for more evenly distributing the tongue weight of a trailer over the front and rear axles of a towing vehicle are well known in the art. A particularly advanced design of weight distributing hitch assembly is disclosed in the assignee's issued U.S. Pat. No. 5,375,872 to Kass et al. entitled "Weight Distributing Hitch". This hitch assembly includes a hitch bar for receipt in a receiver mounted to the vehicle and a ball mount head for mounting on the hitch bar at a selected tilt angle. A pair of spring bars are mounted at their proximal end to the ball mount head. The distal ends of these spring bars are connected by means of cooperating lift units and chains to the frame of the trailer. Such state of the art lift units are exemplified by Reese Products, Inc. product number 21160 incorporating a body that is mounted to the trailer frame, a chain hook with pivoting locking lever and a safety pin for securing the chain hook and lever in an operative position. As is known in the art, the amount of leveling or load transfer to the front axle of the vehicle is adjusted by the selection of the tilt angle of the ball mount head and the engagement of different links of the chains with the chain hooks of the lift units.
While such an arrangement is effective for its intended purpose, it should also be appreciated that the state of the art lift unit connection between the spring bars and trailer frame provides little or no effective means of resisting or controlling trailer sway: that is, undesirable lateral movement of the trailer relative to the towing vehicle. In fact, such sway may arise as a result of a number of factors often encountered during towing operation including uneven, rough and/or winding road conditions; gusty cross-wind weather conditions, uneven trailer loading conditions; and/or result from inherently incompatible trailer and towing vehicle suspension characteristics. Accordingly, a need is also identified for a weight distributing hitch assembly that provides some inherent control of trailer sway to maximize driver confidence, comfort and control during towing.